As a conventional lock structure of a connector, such a lock structure as shown in FIGS. 5 and 6 has been disclosed (see PTL 1). FIG. 5 is a perspective view of an entirety of a lock part, and FIG. 6 is a partial sectional view showing the lock part in a female connector housing.
Both side faces of a lock part 105 in a female connector housing 101 are formed in a shape of a half arrow head extending in a fitting direction, and a releasing lever part 107 is formed of these side faces. In a front end part (an end part at a forehand side in FIG. 5) of the releasing lever part 107, there is formed a front edge part 111 so as to extend over an entire width in a lateral direction. Two lock arms 109 in a plate-like shape are extended backward substantially horizontally from the front end part 111. As shown in FIG. 6, respective back end parts (at a deep side in FIG. 5) of the two lock arms 109 are bent downward, and connected to a horizontal wall part 101a of the female connector housing 101 to be formed into fixed ends 109a. 
An intermediate part of the front edge part 111 between the two lock arms 109 which are spaced in the lateral direction is formed as a latch part (a lock engaging part) 111a for locking a locking part of a male connector housing (not shown).
On the other hand, a lower end part of the releasing lever part 107 is at the substantially same position in the fitting direction as the fixed ends 109a in the back end parts of the lock arms 109, and constitutes a supporting part 107a which performs as a pivot of rotation of the releasing lever part 107 at a time of lock releasing operation. In a state where the female connector housing 101 exists by itself, there is a gap between this supporting part 107a and the horizontal wall part 101a of the female connector housing 101 (See FIG. 6).
A flat face part of the releasing lever part 107 which is spread backward than the supporting part 107a over the entire width constitutes a finger hooking part 117.
According to the lock structure as described above, the releasing lever part 107 for releasing the locked condition between the male connector housing and the female connector housing 101, utilizing a lever action, is provided so as to be continued from the latch part 111a of the lock arms 109. Therefore, when the latch part 111a of the lock arms 109 are deformed by a predetermined amount, occurrence of an excessive stress to be exerted on the fixed ends 109a of the lock arms 109 can be prevented. As the results, the lock arms 109 may be broken.